1. Field of the Invention
The present invention relates to a liquid crystal display (LCD) device which can control a viewing angle.
2. Discussion of the Related Art
Liquid crystal displays, especially, liquid crystal displays using thin film transistors (TFT) as switching devices have been widely used in various applications from mobile phones to large-sized televisions.
In practice, it has been preferable to provide an LCD device having a wide-viewing angle, of which display information can be viewed by a large number of persons.
More recently, there has been proposed a display having the secret mode (for example, Japanese Unexamined Publication No. 5-72529).
FIG. 13 is a view of illustrating a related art LCD device having a secret mode.
Referring to FIG. 13, when using a backlight that emits light to the rear surface of a liquid crystal display panel, the backlight necessarily requires the high directivity.
Between the common liquid crystal display panel and the backlight having the high directivity, there is another liquid crystal display panel for switching between a scattered state and an unscattered state, for example, a polymer dispersed type liquid crystal display panel (a scattering-unscattering switching layer).
When the scattering-unscattering switching layer is in an unscattered state, the light emitted from the backlight proceeds only to the front direction. Thus, if the person is positioned at the side of the liquid crystal display panel, it is impossible for the person positioned at the side to view the displayed image.
On the other hand, if the scattering-unscattering switching layer is in a scattered state, the light emitted from the backlight proceeds to the side directions as well as the front direction. Thus, even though the person is positioned at the side of the liquid crystal display panel, it is possible to view the displayed image. Consequently, a large number of persons can view the image displayed on the liquid crystal display panel.
In this case, it is necessary to fabricate a specific liquid crystal display panel that is different from the common liquid crystal display panel. Therefore, the manufacturing costs are increased.
In order to solve this problem, there has been proposed a related art Fringe Field Switching (FFS) mode LCD device provided with a common electrode having a shape of “<”, to realize a wide viewing angle.
FIG. 14 is a plan view of illustrating each of RGB pixels for a related art FFS mode LCD device. FIGS. 15A and 15B are views of illustrating the operation of liquid crystal molecules according as the voltage is applied to a related art FFS mode LCD device or not.
As illustrated in FIG. 14, the related art FFS mode LCD device includes a common electrode which is formed in shape of “<”, so as to regulate the inclination direction of liquid crystal.
As illustrated in FIG. 15A, if the voltage is not applied to the LCD device, the liquid crystal molecules are aligned in the vertical direction. If the voltage is applied to the LCD device, the liquid crystal molecules are inclined in the predetermined direction based on the effect of the electric field inclined by the common electrode, that is, the direction substantially perpendicular to the extending direction of the common electrode, as illustrated in FIG. 15B. As a result, the liquid crystal molecules are inclined to the two directions corresponding to the “<” shape, whereby the LCD device has the good viewing angle.
However, the related art LCD device has the following problems.
Even though the visibility for the specific direction in the LCD device can be improved resulting from the “<”-shaped common electrode, it is impossible to obtain the display of confidentiality on demand